1. Field of the Invention
The present invention relates to a device that, in order to guarantee originality of a document, uses a paper fiber pattern (hereinafter referred to as “paper fingerprint information”) of paper as identification information on the paper to identify the paper, and on the basis of a result of the identification, controls image processing.
2. Description of the Related Art
There has been proposed a method for preventing an original from being illegally copied on the basis of identification information embedded in the original when the original of an important document such as a contract or certificate is copied. According to the method, it is determined, for example, on the basis of the identification information whether or not the number of times the original has been copied is equal to or more than a predetermined number of times, and if the copying has been performed the predetermined number of times or more, a warning message is issued to a user to make the user select whether to forcedly perform or cancel copying. However, in this method, a digital watermark, IC chip, barcode, or the like should be used to preliminarily add (embed, attach, print, etc.) the identification information to (in, to, on, etc.) the original. Accordingly, it should be appreciated that an original not preliminarily added with identification information cannot be applied with this method.
On the other hand, there has also been a method for preventing illegal copying by using paper fingerprint information of paper as individual paper identification information. Paper is made by entanglement of fine natural fibers, and a degree of the entanglement is random, so that a possibility of existence of pieces of paper having the completely same paper fiber pattern is supposed to be extremely low. Accordingly, the paper fiber pattern can be treated as the paper fingerprint information. The paper fingerprint information has a different characteristic for each sheet of paper, similar to a human fingerprint. As a result, if the paper fingerprint information is used as the individual identification information, it becomes unnecessary to add the identification information to an original with the use of means such as a digital watermark. Also, the paper fiber pattern is not deformed even by being bent to some extent, i.e., it is high in durability, and it changes little with time, so that the paper fingerprint information can be used as the individual identification information for a long term.
In the above method for preventing illegal copying based on the paper fingerprint information, when the paper fingerprint information of the paper is scanned with a scanner, it is necessary to scan the paper with the amount of light for scanning being smaller than that for scanning an image on the paper. That is, when the paper fingerprint information is scanned with the scanner, brightness of a light source should be lower than normal. Accordingly, in the method for preventing illegal copying based on the paper fingerprint information, the scanning operation for the image and that for the paper fingerprint information should be performed separately upon copying of an original, so that there arises a problem of reduction in copying efficiency.